Please follow the below listed instructions to resolve this issue:

Note : Incorrect changes to registry settings can cause serious system problems that may be irreversible without reinstallation of the operating system. You must back up your registry before making any registry changes. We are not responsible for damage resulting from incorrect use of the Registry Editor.
  1. Uninstall the existing Citrix Metaframe client.
  2. Clear the registry of the Citrix Folders stored in the HKEY_ Current_ User Key and stored in the HKEY Local Machine Key.
  3. In Program Files folder on the computer (or on 64-bit machines C:/Program Files (x86)), delete the Citrix folder.
  4. If you are on a Windows 7, Server 2008, or Vista machine, disable the User Account Control.
  5. Reboot your computer.
  6. Download and install the appropriate Citrix client application.
  7. Update your Internet Browser’s Trusted Sites listing to include your Blackbaud Hosting Services site’s URL.
  8. Attempt to launch your hosted application again.
If this issue persists after follow the above steps, please Click Chat with Support and reference this article.